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99 lines
1.8 KiB
Ruby
99 lines
1.8 KiB
Ruby
# The essence of the Mediator Pattern is to "define an object that encapsulates
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# how a set of objects interact". It promotes loose coupling by keeping objects
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# from referring to each other explicitly, and it allows their interaction to be
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# varied independently. Client classes can use the mediator to send messages to
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# other clients, and can receive messages from other clients via an event on the
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# mediator class.
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# Classes witch interact with mediator
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class Buyer
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attr_accessor :balance
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def initialize(balance)
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@balance = balance
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end
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def use_agency_for_buying_house(agency)
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@agency = agency
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end
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def buy(house)
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@agency.purchase(house, self)
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end
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end
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class Seller
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attr_accessor :balance
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def initialize(balance = 0)
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@balance = balance
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end
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def use_agency_for_selling_house(agency, house)
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agency.register house
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end
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end
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class House
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attr_reader :price, :owner
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def initialize(price, owner)
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@price = price
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@owner = owner
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end
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def new_owner(buyer)
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@owner = buyer
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end
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end
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# Mediator class
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class Agency
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def initialize
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@houses = []
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end
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def register(house)
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@houses << house
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end
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def purchase(house, buyer)
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if can_make_deal? house, buyer
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make_payment house, buyer
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change_owner house, buyer
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end
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end
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private
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def can_make_deal?(house, buyer)
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@houses.include?(house) && buyer.balance >= house.price
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end
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def make_payment(house, buyer)
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house.owner.balance += house.price
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buyer.balance -= house.price
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end
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def change_owner(house, buyer)
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house.new_owner buyer
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end
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end
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# Usage
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buyer = Buyer.new(1000)
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seller = Seller.new(0)
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house = House.new(100, seller)
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agency = Agency.new
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buyer.use_agency_for_buying_house agency
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seller.use_agency_for_selling_house agency, house
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buyer.buy house
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puts house.inspect
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